X-RAY DEVICE COMPRISING A RESIDUAL-CURRENT CURCUIT BREAKER

Abstract

The invention relates to a residual-current circuit breaker (31) for an X-ray device. In one embodiment, the residual-current circuit breaker (31) comprises at least one input (34, 36), via which a detector identification signal of a detector identification element (42, 52) can be received, said signal characterising the presence of an X-ray detector and at least one input (35, 37), via which a selection signal for an exposure measurement element (45, 46, 47, 55, 56, 57) can be received, said signal characterising the activation of an exposure measurement element (45, 46, 47, 55, 56, 57). A deactivation signal can be issued via at least one output (38) of the residual-current breaker (31), the deactivation signal being generated as long as a detector identification signal and a selection signal that is assigned to the same detector as the detector identification signal are not received at the same time. FIG. 2

Full Text

Description
The invention relates to an error protection circuit for an x-ray device and an x-ray device with such an error protection circuit. Error protection circuits serve to prevent the emission of high radiation doses due to operating errors.
X-ray facilities have at least one image receiver. The image receiver serves to record x-ray images of a patient or body to be examined, which is fluoroscopically examined by means of the x-ray radiation of an x-ray emitter. In the case of cassette recording points, the image receiver has a cassette drawer, in which a cassette-type x-ray detector is inserted. The x-ray detector can for example be an x-ray film cassette. The cassette drawer also has an exposure measurement chamber, as required to set automatic exposure times. The . exposure measurement chamber has the task of measuring the radiation dose occurring at the x-ray detector and triggering a disconnect signal for the x-ray emitter when a predetermined measurement value is reached.
Cassette drawers and other image receivers can be disposed for example on patient support tables, on C-arms, floor gantries or ceiling gantries. Further possibilities for the arrangement of image receivers are conceivable without further ado. Depending on which x-ray recording points are to be realized, x-ray facilities have one or more image receivers. To produce an x-ray recording, an x-ray detector has to be inserted into the respective image receiver and the x-ray emitter has to be oriented toward the image receiver.
The fact that in principle an x-ray detector does not have to be inserted into every image receiver present and that it also does not have to be possible to identify from outside whether an x-ray detector is inserted, can result in operator errors.
In particular it can happen that the x-ray emitter is switched on, even though there is no x-ray detector inserted into the corresponding image receiver. The radiation dose thereby administered represents a pointless load on the examined patient or body, since no x-ray recording can be produced without an x-ray detector.
In the case of x-ray facilities with a number of image receivers, as well as inserting the x-ray detector it is also necessary to activate an exposure measurement chamber assigned to said x-ray detector. It can therefore happen that an x-ray detector is inserted into the correct image receiver but the exposure measurement chamber assigned to said x-ray detector has not been activated. Possibly an operator erroneously selects the wrong image receiver, even though they have inserted the x-ray detector into the correct image receiver. If an x-ray recording is then initiated using an automatic exposure unit, very high radiation exposure results, as the erroneously selected exposure measurement chamber does not receive any x-ray radiation. Specifically the x-ray radiation strikes the exposure measurement chamber of the correct but not selected image receiver. If the selected exposure measurement chamber does not receive a radiation dose however, it also does not generate a disconnect signal for the x-ray emitter, since the dose limit value is not reached.
To avoid unnecessary radiation exposure due to such operating errors, it is known that the exposure measurement chamber signal can be observed while the x-ray recording is being produced. If after a predetermined time the measurement chamber signal is below a minimum value, incorrect operation is assumed and the x-ray recording is aborted. However modern image receivers are so sensitive that the predetermined minimum value has to be set extremely low. It can therefore happen that the minimum value is exceeded simply by the scattered radiation occurring at the exposure measurement chamber and the x-ray recording is therefore not aborted.
It is also known that in the case of x-ray devices with a central device controller the production of an x-ray recording is only initiated when an x-ray detector is inserted in the selected image receiver. To this end it is only necessary to provide a detector identification, identifying the presence of an x-ray detector in the image receiver. However simple, manual x-ray facilities generally do not have a central controller.
It is known from DE 200 13 478 U1 that it can be checked whether an x-ray detector is inserted in the image receiver and whether the grid contact of the image receiver is closed. A grid contact is provided in the case of image receivers, which have a moving scattered radiation grid. The solution is not suitable for image receivers without or with a fixed scattered radiation grid.
The object of the invention is to allow the prevention of high radiation exposures due to operating errors in a manner that is as economical as possible and can be used in many different ways.
The invention achieves this object by means of an error protection circuit with the features of the first claim and by means of an x-ray device with the features of the sixth claim.
One basic concept of the invention consists of the fact that the error protection circuit has at least one input, by way of which a detector identification signal of a detector identification element can be received, said signal characterizing the presence of an x-ray detector, and at least one input, by way of which a selection signal for an exposure measurement element can be received, said signal characterizing the activation of an exposure measurement element, and also at least one output by way of which a deactivation signal can be emitted, the deactivation signal being generated as a function of receipt of a detector identification signal and a selection signal assigned to the same detector as the detector identification signal. The selection signal thereby indicates which image
receiver has been selected, while the detector identification signal indicates whether an x-ray detector has actually been inserted in the selected image receiver.
This on the one hand avoids an error situation, in which someone has forgotten to insert a detector. On the other hand the error situation, in which an x-ray detector has been inserted into the correct image receiver, but the wrong image receiver has been activated, is also reliably identified. A signal that is available anyway in the x-ray device is used here with the selection signal for the exposure measurement element as the signal for identifying which image receiver is to be used. No other modification of the x-ray device is required for this. The signal of a detector identification element is used as the signal for identifying whether an x-ray detector is inserted. If the image receiver does not make such a signal available anyway, a corresponding sensor or contact can be realized with little outlay.
The error protection system has a logic or logical circuit, which links the detector identification signal to the selection signal, to form the deactivation signal. The logical link essentially only consists of linking the detector identification signal and the selection signal for the same image receiver, such that a deactivation signal is generated, if both input signals are not positive. The deactivation signal can be used by the x-ray device to prohibit the generation of x-ray radiation.
In one advantageous exemplary embodiment the deactivation signal is generated, if a detector identification signal is received but no selection signal assigned to the same detector as the detector identification signal. This signal status indicates that an x-ray detector is inserted but the wrong image receiver has been selected.
In a further advantageous exemplary embodiment the deactivation signal is generated if a selection signal is received but no detector identification signal
assigned to the same detector as the selection signal. This signal status indicates that the right image receiver was selected but someone forgot to insert an x-ray detector.
In a further advantageous exemplary embodiment the deactivation signal is configured to be received by an x-ray generator. This means that the error protection circuit can prohibit the production of an x-ray recording by preventing the x-ray generator applying an x-ray voltage to the x-ray emitter. This prevents the generation of x-ray radiation in a direct manner without involving error-prone means.
In a further advantageous exemplary embodiment the deactivation signal is configured to be received by way of an input of the x-ray generator provided for deactivation signals, e.g. for contact signals. This has the particular advantage that the error protection circuit only has to be connected to an input of the x-ray generator, which is generally present anyway. The input for a door contact signal is generally present, to prevent the initiation of x-ray recordings as long as the door to the control space containing the x-ray controller is not closed. This serves to protect operators from unnecessary radiation exposure. Utilization of such inputs of the x-ray generator that are present anyway means that no modification of the x-ray generator is required. This makes it possible for example to retrofit the error protection circuit easily in already installed x-ray devices.
A further basic concept of the invention consists of an x-ray device with at least one image receiver, having at least one detector identification element, by means of which a detector identification signal can be generated, which characterizes the presence of an x-ray detector, and having at least one exposure measurement element, which can be activated by means of a selection signal generated by the x-ray device, and with an error protection circuit as described above.
Further advantageous exemplary embodiments will emerge from the claims and the description of the figures.
Exemplary embodiments are described in more detail below with reference to the figures, in which:
Figure 1 shows an x-ray facility with a number of image receivers,
Figure 2 shows an x-ray generator with image receivers and an error protection circuit and
Figure 3 shows a logical linking operation within the error protection circuit.
Figure 1 shows an x-ray facility, by means of which different x-ray recording points can be realized. An x-ray recording point here refers to a specific body position of the patient to be examined with associated orientation of the x-ray emitter and image receiver.
The x-ray facility has an x-ray emitter 6, which is supported in a C-arm 1 in such a manner that it can be rotated about a horizontal axis 7. An image receiver 8 is also supported in the C-arm 1.
The C-arm 1 is supported in a ceiling gantry 4 in such a manner that it can be rotated about a horizontal axis 5. The ceiling gantry 4 has possibilities for vertical displacement, rotation and horizontal travel of the ceiling gantry 4. The horizontal travel capacity is indicated by a double arrow 2.
The x-ray facility also has a patient bed 12, supported on a base standing on the floor of the examination room. An image receiver 11 (not shown in further detail) is disposed below the patient bed 12. The image receiver 11 is embodied as a cassette drawer, which can be pulled out in the manner of a conventional drawer
below the patient bed 11, to insert or remove an x-ray detector for example. To utilize an x-ray recording point using the image receiver 11, the C-arm 1 is oriented in such a manner that the x-ray emitter 6 is oriented toward the image receiver 11.
A floor gantry 15 is also provided, also holding an image receiver 14. The image receiver 14 serves to produce x-ray recordings at the standing patient, to which end the x-ray emitter 6 is also correspondingly oriented.
To produce an x-ray recording an operator must position the patient, insert an x-ray detector into the required image receiver 8, 11, 14 and activate the image receiver 8, 11, 14, by selecting the respective exposure measurement chamber.
Figure 2 shows a schematic diagram of an x-ray generator 30 with an error protection circuit 31 and image receivers 40, 50. The corresponding signal connections are also symbolized by arrow lines. The x-ray generator 30 has an input 39 for a deactivation signal. If the x-ray generator 30 receives a positive signal by way of the input 39, generation of an x-ray voltage is prohibited. Prohibiting the generation of x-ray voltage, as required to operate an x-ray emitter, directly prevents the generation of x-ray radiation. The input 39 can for example be the signal input for a door contact.
The image receivers 40, 50 have detector detection elements 42, 52, to identify the respective presence of an x-ray detector. The detector detection elements 42, 52 generate a positive signal, if an x-ray detector is inserted. They emit this signal to corresponding inputs 34, 36 of the error protection circuit 31.
The image receivers 40, 50 also have exposure measurement elements with measurement fields 45, 46, 47, 55, 56, 57. The exposure measurement elements or their measurement fields are activated by a respective selection signal, which is generated by the x-ray generator 30. The respective selection signal serves to
activate at least one measurement field 45, 46, 47, 55, 56, 57 of the image receiver 40, 50, which is to be used to produce an x-ray recording. The selection signal goes to the error protection circuit 31 as well as to the image receivers 40, 50 by way of corresponding inputs 35, 37.
The error protection circuit 31 has a logic (not shown in further detail here), which links the input signals to the inputs 34, 35, 36, 37 as described below.
If the presence of a cassette in the image receiver 40 is detected by the detector detection element 42, at least one of the exposure measurement elements 45, 46, 47 must be selected at the same time, so that no deactivation signal is generated. The selection signals for the exposure measurement elements 45,46, 47 are therefore OR-linked. The result of the OR operation is AND-linked to the signal of the detector detection element 42. The result of the AND linking operation is inverted, to obtain the deactivation signal. It should be noted that a positive signal in each instance means that the x-ray detector is present and respectively an exposure measurement element is selected and respectively the deactivation signal is active. It would be possible to invert the significance of the respective signal without further ado and this would have to be taken into account by a corresponding change to the described logical linking operations. Corresponding changes however result without further ado from the effect of the described logic, so they do not have to be described in more detail here.
If neither a signal of the detector detection element 42 nor a signal of one of the exposure measurement elements 45, 46, 47 is generated in the image receiver 40, the described logical linking of the signals similarly leads correctly to the generation of the deactivation signal.
The signals of the image receiver 50 are linked in the same manner as the signals of the image receiver 40.
Based on a linking of the logical signals, obtained from the individual signals of both image receivers 40, 50, it is possible to identify further incorrect operation situations. If the signal status of both image receivers 40, 50 results in the generation of the deactivation signal, this should actually be generated. If however the signal status of both image receivers 40, 50 results respectively in the suppression of the deactivation signal, it is assumed that both image receivers 40, 50 have been selected and an x-ray detector has been inserted erroneously in each instance. The simultaneous use of both image receivers 40, 50 can however in principle be excluded, since an x-ray emitter can only be oriented toward one of the image receivers. To prevent this incorrect operation situation, the signals for the two image receivers 40, 50 are OR-linked and then inverted. As a result of this linking operation the deactivation signal is only suppressed, if just one image receiver 40, 50 is selected and an x-ray detector is inserted.
Figure 3 shows the described logical link operations in a schematic manner. These linking operations can be extended without further ado to take into account further input variables or changes can be made to adjust to modified incorrect operation situations. In the selected schematic diagram "≥1" means a logical (Boolean) OR operation, "&" means a logical AND operation and "Inv" means a logical inversion (the signal value "1" is inverted to "0" and vice versa).
In one exemplary instance the logical signal "1" is to be present at the signal input 34, indicating the presence of an x-ray detector. The logical signal "1" is also to be present at one of the signals inputs 35, indicating the activation of an exposure measurement element assigned to the x-ray detector. As a result of the OR operation 60, the logical signal "1" is then present. The two signals "1" are linked by the AND operation 61 to the logical signal "1". The subsequent inversion 62 gives the logical signal "0" for this half-side of the overall logic.

The logical signal "1" is also to be present at the signal input 34, indicating the presence of an x-ray detector. However the logical signal "0" is to be present respectively at the signal inputs 35, indicating that none of the exposure measurement elements assigned to the detector have been activated. There is therefore an error situation, where an x-ray detector has been inserted but no associated exposure measurement elements have been activated. The OR operation 70 then results in the logical signal "0". The signals are linked by the AND operation 71 to the logical signal "0". The subsequent inversion 72 gives the logical signal "1" for this half-side of the overall logic.
The logical signal "1" as a result of the inversion 72 results, irrespective of the signal situation of the other half-side of the overall logic, in the OR operation 80 resulting in the logical signal "1". This is generated at the signal output 38 of the error protection circuit 31. The logical signal "1" at the signal output 38 has the same significance as the generation of the deactivation signal by the error protection circuit 31.
The invention can be summarized as follows. The invention relates to an error protection circuit 31 for an x-ray facility. In one exemplary embodiment the error protection circuit 31 has at least one input 34, 36, by way of which a detector identification signal of a detector identification element 42, 52 can be received, said signal characterizing the presence of an x-ray detector, and at least one input 35, 37, by way of which a selection signal for an exposure measurement element 45, 46, 47, 55, 56, 57 can be received, said signal characterizing the activation of an exposure measurement element 45, 46, 47, 55, 56, 57. A deactivation signal can be emitted by way of at least one output 38 of the error protection circuit 31, the deactivation signal being generated on the basis that a detector identification signal and a selection signal assigned to the same detector as the detector identification signal are not received at the same time.

We Claim:
1. An error protection circuit (31) for an x-ray facility by means of which
different x-ray recording points are realised comprising:
- a first input that is operable to receive a detector identification signal of a detector identification element(42, 52), said detector identification signal characterizing the presence of an x-ray detector,
- a second input that is operable to receive a selection signal for an exposure measurement element, said selection signal activating the exposure mea¬surement element, and
- an output that is operable to emit a deactivation signal, the deactivation signal being generated on the basis that a detector identification signal and a selection signal assigned to the x-ray detector as the detector identifica¬tion signal are not received at the same time.

2. The error protection circuit (31) as claimed in claim 1, wherein the deactivation signal is generated, if a detector identification signal and no selection signal assigned to the same detector as the detector identification signal is received.
3. The error protection circuit as claimed in claim 1 or 2, wherein the deactivation signal is generated on the basis that a selection signal and no detector identification signal assigned to the same detector as the selection signal is received.
4. The error protection circuit as claimed in claim 1, wherein the deactivation signal is received by an x-ray generator (30).
5. The error protection circuit as claimed in claim 4, wherein the deactivation signal is received by an input of the x-ray generator provided for deactivation signals.
6. The error protection circuit as claimed in claim 5, wherein the input of the x-ray generator is provided for a door contact signal.
7. An x-ray device with at least one image receiver(40,50), comprising:

- at least one detector identification element(42,52) that is operable to generate a detector identification signal, said signal characterizing the presence of an x-ray detector, and
- at least one exposure measurement element, which is activated by a selection signal generated by the x-ray facility, and
- an error protection circuit comprising,
- a first input that is operable to receive a detector identification signal of a detector identification element, said detector identification signal characterizing the presence of an x-ray detector,
- a second input that is operable to receive a selection signal for an exposure measurement element, said selection signal characterizing the activation of the exposure measurement element, and
- an output that is operable to emit a deactivation signal, the deactivation signal being generated on the basis that a detector identification signal and a selection signal assigned to the x-ray detector as the detector identifica¬tion signal are not received at the same time.